Arabella Sims of Nevada and Egypt's Marwan El Kamash clocked the fastest 800m freestyle times as the U.S. Open began at nine different locations across the country.
Fifteen-year-old Arabella Sims was the standout performer of the first day of the swimming U.S. Open Championships, the first major national event organised by USA Swimming since the start of the coronavirus pandemic.
Sims, of the Sandpipers of Nevada swimming club, clocked 8:27.01 in Irvine, California, to win the women's 800m freestyle event. It was the fifth-fastest time all-time for swimmers in the 15-16 age group.
Her more experienced teammate Erica Sullivan, a member of the USA national team, finished third.
The Championships are being held as a single combined meet with straight finals across nine different cities and states. The times from each of the nine host cities will be compiled to determine the winners of each event.
The top men's 800m free time was set by Egypt's Marwan El Kamash, who swam a personal best 7:52.19 in Indianapolis, Indiana.
Elkamash, a Rio 2016 Olympian who won two African Games gold medals last year, was one of only two men to clear the eight-minute mark.
As well as Irvine and Indianapolis, the other host cities are Beaverton, Oregon; Des Moines, Iowa; Greensboro, North Carolina; Huntsville, Alabama; Richmond, Virginia; San Antonio, Texas; and Sarasota, Florida.
Bobby Finke (7:53.05) was the top American, with the University of Florida 21-year-old setting his time in Sarasota.
Rio 2016 open water competitor Jordan Wilimovsky, who has also qualified for Tokyo 2020 in the same 10 km event, was fifth in 8:01.40 – the top time set in Irvine.
While there are a number of U.S. national team swimmers taking part, a number of big names including Olympic champions Katie Ledecky, Simone Manuel, and Nathan Adrian – all of whom could have competed in Irvine, as they are based in California – chose not to take part.
The meet continues on Friday and Saturday with finals in all Olympic-distance events except the relays.